Small heat pump water heater for tiny house
I’m looking for a small water heater for a net zero 425 square foot tiny house on foundation in climate zone 4A that will have only one full time occupant. I have heard that heat pump water heaters are good for net zero homes, but all the heat pump water heaters that I have come across are like 6 feet tall and I don’t have the space for one. This house will have a 4’ high “conditioned” crawl space however, so something like a small 30 gallon water heater that is about 3 feet tall would work. Is there a product that fits the bill for this situation? If a readymade product is not available, is there a way to create one from products that do already exist …for not a lot of money?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Google "separate heat pump for water heater" and you'll find a couple of options. One is the Nyle Water Heating Systems Geyser.
I don’t think the smaller Nyle heat pumps are on the market anymore. I would love to be proven wrong, but I looked into them a couple of years back and couldn’t find them.
I visited the Nyle website and they show the Geyser c-8 series, but the about page for it links you to a page for you to send them a message. I requested information, so we’ll see how that goes. I’ll report back if I get some.
Here is the response I received from Nyle about the Geyser C-8 series:
“ Thank you for contacting Nyle Water Heating Systems about the Nyle Geyser heat pump water heater. We are excited to tell you that the Geyser is currently out of production for a short period of time while we upgrade the controls to a new, digital platform. We anticipate having units available again in the beginning of the third quarter of 2020... These units are expected to list for $1,400...”
You always dig a small pit in the crawlspace to make room for the taller water heater. Provided there is a floor drain there, should be no problem. Just make sure you have a way to remove it if it needs to be replaced.
What other types of energy are you planning on using? If you are to have a gas or propane stove, why not just get a tankless HW heater? You could also consider a small electric tank, 10- 20 gal which would probably use just as much electricity as a heat pump especially if it's just one person using it and would be more readily available.
I’ve designed other tiny houses that had tankless water heaters, but this one Is a net zero tiny, so no fossil fuels. It will be all electric and tied to the grid, but with a PV system, it should be able to sell back Enough to the grid to achieve net zero. It could possibly be off grid, but I’m not planning on it to be.
Well just be sure the size of your pv system is up to spec.to be grid tied. They are always out to make money so if your system is to small they may not consider it. Check the fine print.
Rheem offers their new Gen 5 hybrid in 40 and 50 gallon sizes that are just over 5 feet tall, though you do need room above to service the filter and attach ductwork (if that's the plan):
https://rmc-cdn.s3.amazonaws.com/media/uploads/iat/sites/36/2020/04/RH-HPE-200_ProTerra_PlumberBrochure_0417B.pdf
Digging a pit as Akos suggested makes sense.
Curious: why do you require a HPWH for such a small home with one occupant? A small well insulated tank type electric might be worth considering.
If you did go with a HPWH and set it up to heat/cool on demand, a significant portion of this tiny home's cooling could come from running the water heater. If not controlled it could lead to over-cooling the space depending when it's running. The Rheem HPWH is 4200 BTU/hr, for example.
Looking for something similar. Did you find something that worked?
I too am looking - I heard a year or more ago that small heat pump HW heaters were coming